Ozone for Waster Water

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Even if you are not familiar with exactly what ozone is, you will at least be familiar with the word. Damage to the ozone layer has been a major environmental concern for decades, and it has been linked to increased global warming and melting ice caps.

The “ozone” in the ozone layer is a very simple molecule. It is O3, or three oxygen atoms bonded together.

This is unusual, of course, because the natural state for oxygen at surface pressure and room temperature is O2, or two atoms bonded together in a molecule.

The result of this is a completely different substance, with a unique set of characteristics and properties. Some of these properties lend ozone rather nicely to the application of wastewater filtration and treatment.

Ozone is added to wastewater during the treatment process, removing germs and organic compounds. In effect, the wastewater is being filtered by the O3 chemical, hence the name ozone filtration.

But there are both advantages and disadvantages to using ozone as a wastewater treatment method.


  • Ozone can be produced on-site using atmospheric oxygen, so the chemical does not need to be brought in.
  • The electricity required to produce the ozone can be generated using renewable methods, at little ongoing cost to the facility.
  • Ozone is renewable as the raw material is simply oxygen from the air at the facility. This also eliminates the need for storage of ozone, as well as reduces the need for storage of other chemicals, such as chlorine, which may be hazardous.
  • Ozone dissolves into oxygen, so there is no potential for hazardous residual chemicals remaining in the wastewater effluent.
  • Ozone has a higher oxidation potential than chlorine.
  • Ozone is more effective at disinfecting both bacteria and viruses from the wastewater.
  • Ozone is more effective than chlorine at removing coloration from the wastewater.
  • Ozone is less likely to form carcinogens during usage.
  • Ozone is effective at lowering the pH of the wastewater.
  • Ozone has a half-life in water of 20 minutes, compared to two to three hours for chlorine.



  • The dosage of ozone has to be correct. If the dose is too low, some germs may survive.
  • The high concentrations required to achieve the correct dose of ozone may be difficult to maintain, as ozone is far less soluble in water than chlorine.
  • Ozone is consumed quickly when reacting with contaminants such as suspended solids. If the water has not been pre-filtered to eliminate these solids, there may not be enough ozone left over to kill all germs.
  • Ozone is highly reactive, which means corrosion-resistant materials must be used during plant construction. The plant must also be designed in a way that protects workers from exposure. Both of these things add to the expense.
  • Production of ozone using the corona method, i.e., passing an electric current through the air between two electrodes, is remarkably inefficient. Around 85% of the energy inputted in the process is wasted as heat energy.
  • If there are bromide salts in the wastewater, ozone can react to create bromate ions and other brominated compounds. These can be carcinogenic.
  • Ozone processing and filtration can be expensive and complex, making it difficult to implement at some smaller plants.


Ozone, if handled correctly, can be a highly beneficial form of wastewater treatment. However, plant managers need to budget carefully to make sure that enough ozone is produced in order to do the job correctly. There may also need to be pre-treatment on the wastewater to get the best out of the process.

Provided that a facility can handle the relative complexity of the process, and bear the cost of operation, ozone filtration is a very viable option.

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